Jack Miller set the fastest time in the first free practice session of the French MotoGP ahead of fellow Ducati rider Johann Zarco on Friday.
These first tests took place on a drying track and in cool, overcast weather, prompting the Australian, who was so impressive in winning the Spanish GP in the last round at the start of the month, to switch briefly to dry tyres
The change, which was not made by the other riders, gave him almost a second and a half on Zarco and he was over two seconds quicker that the rest.
Reigning world champion Joan Mir (Suzuki) was third quickest with his Spanish compatriots, Pol Espargaro and Marc Marquez, both with Honda, tucked in behind.
World championship leader Francesco Bagnaia (Ducati) was seventh Fabio Quartararo, who has won two races on his Yamaha this season, down in 16th.
There will be further practise sessions on Friday afternoon and Saturday morning prior to qualifying on Saturday afternoon.
Timings after first practice
1. Jack Miller (AUS/Ducati) 1:38.007, 2. Johann Zarco (FRA/Ducati) at 1.481, 3. Joan Mir (ESP/Suzuki) 2.062, 4. Pol Espargaro (ESP/Honda) 2.108, 5. Marc Marquez (ESP/Honda) 2.114, 6. Lorenzo Savadori (ITA/Aprilia) 2.237, 7. Francesco Bagnaia (ITA/Ducati) 2.249, 8. Miguel Oliveira (POR/KTM) 2.575, 9. Alex Rins (ESP/Suzuki) 2.672, 10. Aleix Espargaro (ESP/Aprilia) 3.022
Other: 16. Fabio Quartararo (FRA/Yamaha) at 3.634